Piston



ct. 20, 1936. v A, R, BERNARD 2,057,758

PISTON Filed July 27, 1955 Gm @QM Patentednoct. 20, 1936 PATENT orrlcE rls'roN Auguste Louis Ren Bernard, deceased, late of Rueil-Malmaison, France, by Rene Bernard, ne Bournonville, executor, Paris, France 'Application July 27, 1935, serial No. 33,614 In Belgium August 1, 1934 9 Claims.

The present invention relates to pistons of the kind .in which fiuidtightness with respect to the wall of the cylinder in which the piston is moving is obtained by means of expansible packing members. such as split rings. The invention is more especially, although not exclusively, concerned with pistons of this kind for internal combustion engines.

The object of the present invention is to provide a piston of this kind which is better adapted to meet the requirements of practice and, in particulanwhich is so devised that the packing rings are no longer subjected, under the effect of the high pressures acting on said pistons, to exaggerated radial efforts applying them against the wall of the cylinder and involving a rapid wear and tear of said cylinder.

The essential feature of the present invention consists in providing a piston of the type above referred to with an expansible packing ring mounted inside a groove the walls of which are capable of undergoingrelative vdisplacements with respect to one another substantially in the direction of the axis of the piston, in such manner that, under the eifect of the high pressure existing in the cylinder, said-walls tend to move toward each other and compress the packing ring between them thus preventing said pressure from penetrating into the groove.

Other features of the present invention Willv result from the following detailed description of some specific embodiments thereof.

Preferred embodiments of theV present invention will be hereinafter described with reference to the accompanying drawing, given merely by Way of example, and in which:

Fig. 1 is an axial sectional view of a piston for an internal combustion engine made according to the present invention;

Figs. 2 and 3 are half sections of pistons for internal combustion engines made according to two` other embodiments of the invention, respectively.

Assuming, for instance, that the internal combustion engine is of the Diesel type, that is to say has a relatively high ratio of compression, the piston according to the present invention has the following structure:

The general arrangement of the piston may be of any kind whatever permitting the tting of one or more packing members of the type above referred to. However, it seems to be particularly advantageous, for the mounting of the special elements that will be hereinafter described, to provide a piston made of several parts capable 0f being easily assembled together. For instance, as shown in the drawing, the piston includes a head I adapted to be rigidly assembled to a skirt 2, for instance by screwing. Preferably, as shown by way of example in the drawing, these 5 two parts ofqthe piston are assembled together by means of a nut 3 adapted to be screwed inside a cylindrical collar 4 carried by the piston head I, so as-to apply said collar against a flange 5 integral with the skirt 2 of the piston.

The means for ensuring fluid-tightness between the piston and the inner Wallof the cylinder include at least one expansible packing member, such for instance as a split ring 6, mounted in a groove the walls of which pertain to at least two l5 parts capable of undergoing certain relative displacements with respect to each other, substantially in the direction of the axis of the piston, said parts being so arranged that, under the effect of a high pressure inside the cylinder, they tend 20 to move toward each other so as to compress the lateral faces of the pacldng ring, thuspreventing said pressure from penetrating into said groove.

According to the embodiments shown by the 25 drawing, this groove is devised in such manner that its lower lateral wall 1 is carried by the piston proper, that is to say by the skirt 2 of said piston, said wall of the groove consisting advantageously of the upper edge of said skirt 2, where- 30 by the machining, and even the grinding thereof, is easily performed.

As for the other lateral wall of the groove. to wit the upper wall 8 of said groove, and also the bottom 9 of said groove, they are carried by a 35 member capable of undergoing certain axial displacements With respect to the piston, said member being arranged in such manner that the pressure inside the cylinder tends to apply the member in question laterally against the packing ring, 40 which is thus compressed between walls 1 and 8, whereby said pressure in the cylinder is, for'praclil . tical purposes, prevented from penetrating to the inner cylindrical wall of the packing ring.

Consequently, according' to preferred embodi- 45 ments of the invention, the pistonproper being made as above explained, this. axially movable member consists of a closed ring, advantageously made of stainless steel and of t-shaped cross section.

Said member includes, on the one hand, a cylindrical part i0, coaxial with the piston and adapted to -be tted freely around the collar 4 of the piston head, with, for instance, a play ranging between 0.2 mm. and 0.3 mm. (in the radial 5,',

direction) between these` two parts 4and `10. The outer cylindrical wall of said element' 'I0 constitutes, over a portiorrof its height, the bottom 9 of the groove. The lower portion of said part Illis engaged, over a,suitable height, for instance a height equal to thatV of a packing ring',

in a'n annular groove provided between collar d and a cylindrical edge II adjacent to wall '1, a play of, say, 0.01 mm. (still in the radial direction)'being provided between walls 3 andi I.

Said axially movable member'further includes an annular flange I2 extending in the outward direction, the wall 8 of saidange which isturned Y toward the inside of the groove in which packing member 6 is to be housed being adapted to t in a iiuidtight manner on the corresponding face of said packing ring.

In'order to maintain this ring-shaped member in position While allowing it to move axially in the desired manner, either. of the following arrangements may be employed: 'Y I In the embodiment shown by Fig. l, the piston head includes an annular ange i3 which partly .covers said ring I2 and the whole is devised'in such manner that, after the' parts have been assembled together, there remains, between this flange and the upper edge of ring i2, a play of,

say, 0.2 mm.. I .v In the embodiment of Fig. 2 and in thatl of Fig. 3, cylindrical part 4III isinwardly threaded on a portion. of its height, for instance the lower half thereof, the threads being, for instance of square or slightly trapezoidal Vcross section. The cor,-

responding portion of the outer wall of collar d is V provided with threads of the same shape and pitch, a longitudinal play of, say, 0.2"mm, 'being provided between, the threads of the two parts,

and means, such for instance as a lug (Fig. 3),

being provided for preventing, after the parts have been' assembled, member I I? from unserew ing.. Of course-these arrangements are given merely by way of example and the invention is not limited to these specic features. Forinstance a bayonet joint might also be used.

It' will be readily understood that, in the case of -arrangements corresponding to the-last memf tioned .embodiments (Figs. 2 and-3) itis unneci -essary to provide the piston head with a iilange such as I3 (Fig. 1). Onthe contrary, ring I2 shall be so shaped thatits external surface prol longs that of the piston head.

In the embodiment of Fig. 2, this ring I2 is ofV wedge-shaped cross section in order that, in the case of an engine providedwith portsfthe feed may be controlled by the upper edge of the iirst packing ring 6.

On the contrary, in the embodiment of I iig.-.3,`V

the upper face of ring I2 is substantially at rightangles to the axis of the piston, so that said ring has a', certain thickness at its periphery.

. Besides, it should be noted that the whole of the piston head, collar 4, and the pistonskirt might consist of a single element.

In any case, and whatever be the means that are made useof for keeping ring Iii- I2 in position, ring-shaped iange I2 may be made of two parts, as shown in Fig. 3wall 8 being, in this case carried by a ring` I4 (which, preferably, is not a split ring) disposed immediately above split ring 6.

When the piston head does not include a flange I3, the upper part of element I0 is preferably provided, as shown by Fig. 3, with an external ange I5, preferably of an outerdiameter smaller than that of the piston, the whole beingl designed in such manner that', after -the parts have been assembled together, the upper face of this iiange I5 is flush with the upper surface of the piston head and is, preferably, 'located at the leveLof 'the upper edge of ring I4 (for this-purpose, the upper portion rof said ring I4 shall be provided with a suitable annular housing) .v

Whatever be the spec'ic arrangement.` that is chosen, above split ringii there will be provided va non-split ring (element 8) the upper 1face`of which is iiush with the upper surface ofthe piston head at the periphery thereof, said nonfsplit ring' beingl capable of coacting with the ports of the cylinder for controlling tha feed to-the cylinde1. l j

In any case, these non-split ring and split ring shall be strongly applied against each other when ring I2 ispusheddownwardly and onthe contrary there shall be a total play of, say, 0.2,

mm. between "them' when ring I2 is moved upi wardly.

Preferably, in rder to prevent gas leakage as might take. place between ele'i'nent I0. and the piston,'or, more laccuratelyf part 6 of said piston, one of these partsmay be provided with packing rings Iii adapted-to be applied against thecther part after the vwhole is assembled together (Figs.

V2 and'3) These packing rings are, for instance, carried by the outer facev of collar 4 so as to be applied against the upper 'part of the inner. wall oi element III.y e

Advantageously, these packing rings are so devised as to be applied very strongly against the Aopposite part, this being not objectionable since y no important relative displacement is to takev place between the parts.

It is then possible to provide, between walls 9 and' I I, a more considerable play as if packing rings I6 did not exist, for instance aplayof'OZ i Finally, concerning th e depth Qfffthegroove left between the elements'ab'ove mentioned, which groove is intended to 'receive packing ring 6, said groove is so dimensioned .as to leave a certain play, of for instance 0.3 mm., between the inner faceof the packing ringv d and the bottom -9 of the groove.

The piston according to the present invention,v yas above described, has the following advantages:

Considering this piston during its compression stroke, `it may be assumed, in the application that is considered, that the combined effects of pressure and inertia tend to 'maintain said ring-A shaped element Ill--I 2 constantly applied against .the packing ring. This is due to the fact that the pressure is sufiicientlyhigh, during the last matter of fact, the gases vunder high` pressure.n

cannot penetrate into the bottom of the groove,

- neither between the packing ring andy wall 8 nor between ange II 'and wall 9.

This arrangement does not prevent the packing ring from playing its normal part due to its elasticity since, for some positions of the piston, for instance at mid-stroke during compression, the force applying element Ill-I2 against the packing ring shall be relatively small. Furthermore, in the case of a four-stroke engine, the packing ring shall be quite free during considerable portions of the inlet and exhaust strokes. This packing ring shall therefore be placed under conditions in which it is capable of ensuring uid tightness between the piston and the cylinder.

It should further be noted that ring-shaped member lil-I2 also acts as a screen with respect to the packing ring and protects it against the eifects of high temperatures.

I may eventually provide, at the periphery of the piston, and below packing ring 6, ordinary packing rings I1 which, as a matter of fact, are wholly protected against the action of high pres- SureS.

It should also be understood that more than one packing ring such as 6 might be provided in the groove.

Finally, it may be useful, i'n some cases, instead ofv wholly cutting oil the connection between the inside of the groove and the cylinder, to admit gases at a certain pressure into said groove, for instance with a view to scavenging the deposits that might have accumulated at the bottom of said groove, according to a feature already described, for instance, in my Belgian Patent No. 315,335- of June 15, 1934. For instance, in order to obtain this result, member Ill is provided with one of several passages I8, of very small section, of radial or oblique direction. Of course, when packing rings I8 are provided, passages I8 must be located above said packing rings.

It stands to reason that the invention is also applicable to explosion engines.

In a general manner, while I have, in the above description, disclosed what I- .deem to be practical and eicient embodiments of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the appended claims.

What I claim is;

l. A piston for use in a cylinder, comprising, in combination, a piston body including a piston head and a piston skirt rigid with said piston head and provided with an annular shoulder in its periphery, at least one annular circumferentially continuous structure movable axially with respect to said piston skirt forming an annular part of the face of the piston head and forming an annular groove between itself and said shoulder, said structure including an annular member of L-shaped section, one of the branches or the L comprising a cylindrical portion which forms,

for at least a portion of its length, the bottom of said groove, and the other branch being parallel to the lateral inner wall of the groove opposed to said shoulder. and at least one split metallic packing ring mounted in said annular groove, the coacting surfaces forming the lateral inner walls of said groove and the lateral walls of said packing ring respectively lying in planes vertical to the axis of the cylinder, whereby said annular member is moved toward said ring by the pressure of the gases in said cylinder so as to clamp said packing ring between said shoulder and said annular member.

2. A piston according to claim 1, including packing means between the inner surface of the cylindrical portion of said annular member and 3. A piston according to claim 1 in which said piston head and said piston skirt areprovlded with a cylindrical groove coaxial with said piston therebetween, the end of the cylindrical portion of said annular member being mounted in said last mentioned groove.

4. A piston according to claim 1 further including a. cylindrical part integral with said piston head and iltting coaxially in the cylindrical part of said annular member and packing rings mounted in one of said cylindrical parts and bearing against the other cylindrical part.

5. A piston according to claim 1 having an outwardly extending flange on the peripheral portion of said piston head partially overlapping the annulus-shaped portion of said annular member and-spaced axially therefrom.

6. A piston according to claiml having a cylindrical part integral with said piston head fitting coaxlally in the cylindrical part of said annular member and slightly spaced therefrom and coacting threads on the adjacent' faces of said cylindrical parts, said threads permitting a limited axial play of said cylindrical parts with respect to each other.

7. A piston according to claim -1 having a y ring-shaped member interposed between the inner face of the annulus-shaped part of said annular member and said packing ring.

8. A piston according to claim l having a ring-shaped member interposed between the inner face of the annulus-shaped part of said annular member and said packing ring, said ringshaped member projecting beyond the peripheral edge of said annulus-shaped part so as to be substantially at the same level as the upper face thereof, the upper face of said annular member being substantially iiush with the outer face of said piston head.

.9. In a piston according to claim l, said cylindrical part of the annular member having passages of small section therethrough, whereby to admit gases at a limited pressure into the bottom of saidvgroove.

RENE BERNARD, mi: BoURNoNVnLn, Ezecwtor of Auguste Louis Ren Bemard, Deceased. 

